This invention is directed at a method for detecting the presence of alcohols in hydrocarbon samples. More specifically, the present invention is directed at a colorimetric method for detecting the presence of alcohol in gasoline.
Frequently, it is necessary to determine if alcohol is present in hydrocarbons, such as gasoline. Alcohols, such as methanol, ethanol, and tertiary butanol, often are added to the gasoline pool to improve octane. However, the presence of alcohol, particularly in excess of about 1 volume percent, may cause several adverse effects. Since the alcohols are oxygenated compounds, their presence in gasoline may affect the oxygen to fuel ratio of the fuel being combusted leading to potential operational and emission problems. As a result, the United States Environmental Protection Administration currently limits the oxygen content of gasoline to less than 2 weight percent, (or up to 0.3 volume percent methanol) unless specific waivers have been granted.
In addition, the presence of excessive quantities of alcohol in gasoline may cause increased engine corrosion and adversely affect elastomeric engine seals.
In other instances, as for example in performing vapor pressure tests to determine the volatility of gasoline, the validity of test results may be dependent on the absence of alcohols. Tests which tolerate the presence of alcohols tend to be more elaborate and more expensive to perform. Hence, these alcohol-tolerant tests normally are conducted only when alcohols are known to be present in the sample tested.
Present methods for detecting the presence of alcohol in gasoline tend to be rather expensive, and usually require the use of elaborate analytical equipment operated by highly trained technicians. These methods are not readily adaptable for use by non-technically trained individuals in the field.
U.S. Pat. No. 4,070,154 discloses a method for measuring the alcohol content in jet fuel by mixing a known quantity of jet fuel with a known amount of an emulsion comprising a gel of finely grained particles saturated with a solution of sodium vanadiate, 8 hydroxyquinoline, water, acetic acid and an organic solvent which is free of OH-group chemicals and insoluble in water to form an emulsion matrix. The patent discloses that this mixture can be stored in a tube prior to use. A series of standards are prepared by preparing fuel samples with various known alcohol concentrations and passing these samples through tubes containing the mixture. The extent to which the emulsion matrix changes color in each standard tube is noted. The alcohol content of the fuel then is determined by adding a predetermined quantity of fuel to the mixture and noting the amount of the mixture that is discolored. This procecdure is not generally used because of the rather elaborate preparation required.
U.S. Pat. No. 2,968,940 discloses a method for detecting dispersed water in jet fuel and similar hydrocarbon oils, by contacting the fuel with a small amount of a mixture of finely divided, water-soluble, solid anhydrous dye and a finely-divided solid capable of taking up or adsorbing any water present in the sample. The dye required is the sodium salt of o-cresolsulfonphthalein and the finely divided solids were required to be anhydrous barium carbonate. Samples of the dye and finely divided solid are added to a sample of the fuel and agitated. The intensity of the color of the sample is compared with that of samples of known dispersed water content to determine the approximate dispersed water content of the sample. U.S. Pat. No. 3,505,020 discloses the use of a minor portion of fuchsia dye and a major proportion of a finely-divided, substantially anhydrous solid, i.e., calcium carbonate, barium carbonate, barium sulfate, magnesium carbonate and combinations thereof, to determine the approximate dispersed water content in jet fuels and similar hydrocarbon oils. A sample of the hydrocarbon is contacted with the dye-anhydrous solid mixture and agitated. The color change may be observed and compared to samples having known dispersed water contents to determine the approximate dispersed water content of the sample. The test procedures of these two U.S. patents may not be directly applicable to determining the alcohol content of gasoline, which often has a higher dissolved water content than the middle distillate fuels, such as jet fuel, since free water present would interfere with the test procedure for determining the alcohol content.
Accordingly, it would be desirable to provide a process which is a reliable, and inexpensive test for determining the presence of alcohol in hydrocarbon samples, such as gasoline.
It also would be desirable to provide a process which is easily used by non-technically trained individuals.
It also would be advantageous to provide a process which could be utilized in the field for qualitative screening of hydrocarbons, such as gasoline, for alcohol presence without the necessity of sending all samples for detailed analysis.
The present invention is directed at a method for determining the presence of alcohols, such as methanol, ethanol, the propanols and the butanols, in a hydrocarbon, such as gasoline, and comprises contacting the hydrocarbon with a mixture comprising:
A. an alcohol soluble, hydrocarbon insoluble dye; and,
B. an alcohol insoluble, hydrocarbon insoluble solid, and noting whether the mixtrue changes color. A color change indicates the presence of alcohol.